Commit 142781e1 authored by Thomas Gleixner's avatar Thomas Gleixner

entry: Provide generic syscall entry functionality

On syscall entry certain work needs to be done:

   - Establish state (lockdep, context tracking, tracing)
   - Conditional work (ptrace, seccomp, audit...)

This code is needlessly duplicated and  different in all
architectures.

Provide a generic version based on the x86 implementation which has all the
RCU and instrumentation bits right.

As interrupt/exception entry from user space needs parts of the same
functionality, provide a function for this as well.

syscall_enter_from_user_mode() and irqentry_enter_from_user_mode() must be
called right after the low level ASM entry. The calling code must be
non-instrumentable. After the functions returns state is correct and the
subsequent functions can be instrumented.
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200722220519.513463269@linutronix.de
parent 6823ecab
......@@ -27,6 +27,9 @@ config HAVE_IMA_KEXEC
config HOTPLUG_SMT
bool
config GENERIC_ENTRY
bool
config OPROFILE
tristate "OProfile system profiling"
depends on PROFILING
......
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_ENTRYCOMMON_H
#define __LINUX_ENTRYCOMMON_H
#include <linux/tracehook.h>
#include <linux/syscalls.h>
#include <linux/seccomp.h>
#include <linux/sched.h>
#include <asm/entry-common.h>
/*
* Define dummy _TIF work flags if not defined by the architecture or for
* disabled functionality.
*/
#ifndef _TIF_SYSCALL_EMU
# define _TIF_SYSCALL_EMU (0)
#endif
#ifndef _TIF_SYSCALL_TRACEPOINT
# define _TIF_SYSCALL_TRACEPOINT (0)
#endif
#ifndef _TIF_SECCOMP
# define _TIF_SECCOMP (0)
#endif
#ifndef _TIF_SYSCALL_AUDIT
# define _TIF_SYSCALL_AUDIT (0)
#endif
/*
* TIF flags handled in syscall_enter_from_usermode()
*/
#ifndef ARCH_SYSCALL_ENTER_WORK
# define ARCH_SYSCALL_ENTER_WORK (0)
#endif
#define SYSCALL_ENTER_WORK \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU | \
ARCH_SYSCALL_ENTER_WORK)
/**
* arch_check_user_regs - Architecture specific sanity check for user mode regs
* @regs: Pointer to currents pt_regs
*
* Defaults to an empty implementation. Can be replaced by architecture
* specific code.
*
* Invoked from syscall_enter_from_user_mode() in the non-instrumentable
* section. Use __always_inline so the compiler cannot push it out of line
* and make it instrumentable.
*/
static __always_inline void arch_check_user_regs(struct pt_regs *regs);
#ifndef arch_check_user_regs
static __always_inline void arch_check_user_regs(struct pt_regs *regs) {}
#endif
/**
* arch_syscall_enter_tracehook - Wrapper around tracehook_report_syscall_entry()
* @regs: Pointer to currents pt_regs
*
* Returns: 0 on success or an error code to skip the syscall.
*
* Defaults to tracehook_report_syscall_entry(). Can be replaced by
* architecture specific code.
*
* Invoked from syscall_enter_from_user_mode()
*/
static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs);
#ifndef arch_syscall_enter_tracehook
static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs)
{
return tracehook_report_syscall_entry(regs);
}
#endif
/**
* syscall_enter_from_user_mode - Check and handle work before invoking
* a syscall
* @regs: Pointer to currents pt_regs
* @syscall: The syscall number
*
* Invoked from architecture specific syscall entry code with interrupts
* disabled. The calling code has to be non-instrumentable. When the
* function returns all state is correct and the subsequent functions can be
* instrumented.
*
* Returns: The original or a modified syscall number
*
* If the returned syscall number is -1 then the syscall should be
* skipped. In this case the caller may invoke syscall_set_error() or
* syscall_set_return_value() first. If neither of those are called and -1
* is returned, then the syscall will fail with ENOSYS.
*
* The following functionality is handled here:
*
* 1) Establish state (lockdep, RCU (context tracking), tracing)
* 2) TIF flag dependent invocations of arch_syscall_enter_tracehook(),
* __secure_computing(), trace_sys_enter()
* 3) Invocation of audit_syscall_entry()
*/
long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);
/**
* irqentry_enter_from_user_mode - Establish state before invoking the irq handler
* @regs: Pointer to currents pt_regs
*
* Invoked from architecture specific entry code with interrupts disabled.
* Can only be called when the interrupt entry came from user mode. The
* calling code must be non-instrumentable. When the function returns all
* state is correct and the subsequent functions can be instrumented.
*
* The function establishes state (lockdep, RCU (context tracking), tracing)
*/
void irqentry_enter_from_user_mode(struct pt_regs *regs);
#endif
......@@ -48,6 +48,7 @@ obj-y += irq/
obj-y += rcu/
obj-y += livepatch/
obj-y += dma/
obj-y += entry/
obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
obj-$(CONFIG_FREEZER) += freezer.o
......
# SPDX-License-Identifier: GPL-2.0
# Prevent the noinstr section from being pestered by sanitizer and other goodies
# as long as these things cannot be disabled per function.
KASAN_SANITIZE := n
UBSAN_SANITIZE := n
KCOV_INSTRUMENT := n
CFLAGS_REMOVE_common.o = -fstack-protector -fstack-protector-strong
CFLAGS_common.o += -fno-stack-protector
obj-$(CONFIG_GENERIC_ENTRY) += common.o
// SPDX-License-Identifier: GPL-2.0
#include <linux/context_tracking.h>
#include <linux/entry-common.h>
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
/**
* enter_from_user_mode - Establish state when coming from user mode
*
* Syscall/interrupt entry disables interrupts, but user mode is traced as
* interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
*
* 1) Tell lockdep that interrupts are disabled
* 2) Invoke context tracking if enabled to reactivate RCU
* 3) Trace interrupts off state
*/
static __always_inline void enter_from_user_mode(struct pt_regs *regs)
{
arch_check_user_regs(regs);
lockdep_hardirqs_off(CALLER_ADDR0);
CT_WARN_ON(ct_state() != CONTEXT_USER);
user_exit_irqoff();
instrumentation_begin();
trace_hardirqs_off_finish();
instrumentation_end();
}
static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
{
if (unlikely(audit_context())) {
unsigned long args[6];
syscall_get_arguments(current, regs, args);
audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
}
}
static long syscall_trace_enter(struct pt_regs *regs, long syscall,
unsigned long ti_work)
{
long ret = 0;
/* Handle ptrace */
if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
ret = arch_syscall_enter_tracehook(regs);
if (ret || (ti_work & _TIF_SYSCALL_EMU))
return -1L;
}
/* Do seccomp after ptrace, to catch any tracer changes. */
if (ti_work & _TIF_SECCOMP) {
ret = __secure_computing(NULL);
if (ret == -1L)
return ret;
}
if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
trace_sys_enter(regs, syscall);
syscall_enter_audit(regs, syscall);
return ret ? : syscall;
}
noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
{
unsigned long ti_work;
enter_from_user_mode(regs);
instrumentation_begin();
local_irq_enable();
ti_work = READ_ONCE(current_thread_info()->flags);
if (ti_work & SYSCALL_ENTER_WORK)
syscall = syscall_trace_enter(regs, syscall, ti_work);
instrumentation_end();
return syscall;
}
noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
{
enter_from_user_mode(regs);
}
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